An experimental method of presenting the principles determining the general properties of optical gratings

In a laboratory which is not well equipped with modern optical instruments, the actual appearance and meaning of many of the phenomena whose theory is studied is not in the least appreciated. This seems especially the case in connection with the elements of the more advanced theory of optical gratings, and with the theory of interference spectroscopes.
The following presentation is an attempt to provide a set of experiments, made with fairly cheap and simple apparatus, which shall illustrate the various effects that produce the phenomena exhibited by an optical grating, and includes such simple theoretical discussion as is necessary to understand the experiments.
In the course of the experiments the effects that determine such things as the resolving power of a grating, the intensity of the spectrum of a given order, and so on, are directly observed. At the end of the paper the results obtained in the discussion are applied to the cases of the ordinary plane grating and the Michleson Echelon.